1. Field of the Invention
The present invention relates to a safety relay with restricted guidance contacts for network voltage and an insulation between the control side and the output side that is sufficient for explosion endangered regions, in particular a print relay, according to the preamble to claim 1.
2. Background Information
There are known dual-contact and multi-contact print relays on the market that are for network voltage and have restricted guidance contacts, in which at least one contact spring pair is disposed on one side and on the other side of a partition, and the insulation between the individual output side contacts is increased or doubled in order to achieve a so-called "safe separation" according to DIN VDE 0106 (DIN VDE German Institute for Standardization, Association of German Electrical Engineers) protection from dangerous body currents). Furthermore, an insulation that fulfills the requirements for electrical equipment for explosion endangered regions according to the standard EN 50020 is provided between the control side and the output side (leakage path on the inside of the relay .gtoreq.10 mm, referred to below as EEx insulation). Relays of is kind are known, for example from the 1998 product catalog of the present assignee. In it, they are called SIR 312 or SIR 422, for example. These relays, with 46.4 or 58.9.times.16.times.30.7 mm are already relatively small for four-contact or six-contact safety relays. But users continue to demand the smallest relays possible. With increasing miniaturization, however, maintaining the required safety distances is becoming increasingly difficult. In many cases, the guidance of the contact springs in a straight line is forsaken in favor of smaller dimensions and therefore a good and long-lasting adjustment is made more difficult.
Thus, for example, there is a four-contact relay on the market with very small outer dimensions of approx. 36.times.12.5.times.29 mm, but without EEx insulation between the control and output sides. Also, the output side plug connectors of different contact pairs have no doubled insulation. With this relay, in order to achieve these small dimensions, the contact springs are each bent twice between the base and the top part. In addition, they are more strongly offset the closer to the coil they are disposed.
U.S. Pat. No. 4,618,842 has disclosed a relay without restricted guidance, which likewise has two change-over contacts on opposite sides of a partition that perpendicularly adjoins the control part. The contact springs of the contact units, which are likewise offset, are moved in one direction by means of a comb which is divided into two arms and is driven by an armature and a magnet coil. Pins are embodied on the arms and engage in rectangular holes in the moved ends of the contact springs. The comb can be introduced in the drive direction, with these pins being inserted into these holes. The partition has an insertion aid, not described in detail, between the two arms of the comb. The insertion aid constitutes a thickening of the partition and is disposed with a sufficient distance from the moved contact spring so that with the insertion of the comb, the pins are aligned before they have to be slid into the holes. The insertion aid therefore has a rounded end, which is disposed on the control side with a greater distance from the moved contact spring than the partition between the control side and the output side is spaced apart from the moved contact spring. The relay has no EEx insulation.
However, there are known change-over contact relays with EEx insulation between the control side and the output side, which have this small size, in particular, the one listed in the above-mentioned catalog of the present assignee, under the name SIR 282. In this one, the coil, together with the core and yoke, as well as the base ends of the contact springs, are cast integrally into a carrier part so that the relay is wash-resistant. The armature is disposed on the side of the coil remote from the output side. The three contact springs of a change-over contact unit are disposed very close to one another, wherein the central moved contact spring extends in a straight line through the insulating carrier part and constitutes the plug connector on the outside of the carrier part. The two other contact springs, however, are each offset in the integrally cast region by a good 2.5 mm in order, despite the very close disposition of the contact springs, to maintain a norm-dictated distance of approx. 5 mm between the plug connectors of the contact springs of a change-over contact. The partition between the two change-over contacts is disposed in the region of the moved ends of the contact springs, between two short ribs on the cap. As a result, the air and leakage paths between the one contact spring of a change-over contact and the diagonally opposing contact spring of the other change-over contact are long enough to assure an increased insulation under certain conditions.
For the assembly of this relay, the contact springs must be inserted into a pre-assembled holding part. Then this holding part, which is equipped with contact springs, together with the magnet coil, core, and yoke, can be cast into a single part in an injection molding facility.
Apart from the insufficient properties of the change-over contact relay for corresponding to the current requirements for relays in explosion endangered regions, the offsets of the contact springs are particularly disadvantageous. It is also disadvantageous that the carrier part has to be manufactured by means of two separate casting processes.